Argumentation activities in the science classroom bring students' social relationships to the forefront, which can make it difficult for a student who is marginalized in peer relationships to participate in discussions. In this study, we qualitatively analyzed how a marginalized student's attempts to position himself as an accepted member of small-group argumentation activities were constrained or afforded by other group members in a Korean science classroom. The results show that the students limited the marginalized student's participation by shifting to unproductive framing. The following two features were identified when the marginalized student's ideas were addressed in the discussions: (a) his idea was acknowledged as being closer to group members' understanding of the argumentation activity in the science classroom, and (b) he invited the other students to modify his understanding. This study's findings provide useful information for designing instructional strategies that provide equitable learning opportunities in argumentation activities in the science classroom.